In recent years, there are mobile terminals such as mobile phones that employ an input apparatus having a touch sensor such as a touch panel, a touch switch and the like, as an input apparatus such as an operation unit, a switch and the like for detecting a contact operation by a user. Such an input apparatus having the touch sensor is popularly used for not only the mobile terminals but also information equipment such as calculators and ticket vending machines, home electric appliances such as microwaves, TV sets and lighting equipment, industrial equipment (FA equipment) and the like.
There are known a variety of types of those touch sensors, such as a resistive film type, a capacitive type, an optical type and the like. However, touch sensors of these types receive a contact operation by a finger or a stylus pen and, unlike push-button switches, the touch sensors themselves are not physically displaced when touched.
In contact operation to the touch sensor, therefore, the operator is not able to obtain feedback to the contact operation. Without an operation feeling in contact operation, the operator has no means of knowing whether the contact operation is appropriately detected by the terminal. When using such a terminal, accordingly, the operator is likely to repeat the contact operation at the same position, which may cause stress on the operator.
In order to prevent such unnecessary repeated contact operations, there is known an apparatus which, for example, generates sound when the terminal appropriately recognizes the contact operation. There is also known an apparatus which changes a display state by, for example, changing color of a user interface input object (hereinafter, referred to simply as an “object”) such as an input button graphically depicted in a display unit at a position corresponding to a position where the contact operation is detected. These apparatuses allow the operator auditory or visual confirmation on whether the contact operation is appropriately detected by the terminal.
However, such auditory feedback may be difficult to be confirmed in a noisy environment and is not applicable when the apparatus being used is in a silent mode. Moreover, in using such visual feedback, if the object displayed on the display unit is small, the operator may not be able to confirm the change in the display state, as a view of the object is blocked by the finger, particularly when the operator performs the contact operation with the finger.
As such, there is suggested a feedback method relying on neither auditory-nor visual sensation but instead vibrating the touch sensor when the touch sensor detects a contact (for example, see Patent Documents 1, 2).